The spinal cord is a long, cylindrical structure of nervous tissue that forms a vital part of the central nervous system. It extends from the lower part of the medulla oblongata at the base of the brain and continues downward through the vertebral canal, usually terminating around the level of the first or second lumbar vertebra. In biopsychology, the spinal cord is of central importance because it serves as the primary pathway for communication between the brain and the rest of the body, and it is also capable of integrating many reflexive and automatic behaviors independently of conscious control. An illustration of the spinal cord in cross-section reveals its fundamental structural organization. At the center lies a small central canal filled with cerebrospinal fluid. Surrounding this canal is a butterfly-shaped or H-shaped region known as gray matter. This gray matter contains neuron cell bodies, dendrites, and unmyelinated axons. The gray matter is divided into anterior (ventral) horns and posterior (dorsal) horns, and in some regions, lateral horns. The anterior horns contain motor neurons that send impulses out to skeletal muscles. The posterior horns receive sensory information from peripheral sensory neurons. The lateral horns,